About a 20-minute walk to the northwest of the airstrip are Grupo B and Grupo A, the latter featuring the more formidable structures around the city's main square. Palacio V, on the east side of the square, is considered a model for Tikal's North Acropolis. In 1916 the American archaeologist Sylvanus Morley uncovered a stele dating from the 8th baktún (Maya calendar term) at Grupo A. Thus the site was called Uaxactún, meaning 'eight stone.'